Optically active ketals, processes for their preparation and their use in the synthesis of alpha-arylalkanoic acids

Alkyl aryl-ketal having the formula ##STR16## wherein R.sub.1 and R.sub.2 each independently represent hydroxy, O.sup.- M.sup.+, OR.sub.3 or ##STR17## R.sub.3 represents C.sub.1 -C.sub.24 alkyl, C.sub.3 -C.sub.6 cycloalkyl, phenyl or benzyl,

• M.sup.+ represents the cation of an alkaline metal,
• R.sub.4 and R.sub.5, each independently, represent hydrogen, C.sub.1 -C.sub.4 alkyl, C.sub.5 -C.sub.6 cycloalkyl, (CH.sub.2).sub.n --CH.sub.2 OH wherein n equals 1, 2 or 3, or R.sub.4 and R.sub.5 together represent (CH.sub.2).sub.m wherein m equals 4 or 5, or CH.sub.2 --CH.sub.2 --R.sub.6 --CH.sub.2 --CH.sub.2 wherein R.sub.6 represents O, NH or N--(C.sub.1 -C.sub.4) alkyl,
• X represents chlorine, bromine, iodine, hydroxy, carboxylic acyloxy, alkylsulphonyloxy or arylsulphonyloxy,
• Z represents hydrogen, methyl or alkaline metal, and
• Y is hydrogen, chlorine or bromine,
• the carbon atoms marked by an asterisk being both in configuration R or S.

Alkyl aryl-ketal of the formula ##STR18## wherein Ar represents naphthyl, 6-methoxy-2-naphthyl, 5-chloro-6-methoxy-2-naphthyl, 5-bromo-6-methoxy-2-naphthyl, 6-hydroxy-2-naphthyl, 5-bromo-6-hydroxy-2-naphthyl and 5-chloro-6-hydroxy-2-naphthyl,

• R represents C.sub.1 -C.sub.4 alkyl,
• R.sub.1 and R.sub.2 each independently represent hydroxy, O.sup.- M.sup.+, OR.sub.3 or ##STR19## R.sub.3 represents C.sub.1 -C.sub.24 alkyl, C.sub.3 -C.sub.6 cycloalkyl, phenyl or benzyl,
• M.sup.+ represents the cation of an alkaline metal,
• R.sub.4 and R.sub.5, each independently, represent hydrogen, C.sub.1 -C.sub.4 alkyl, C.sub.5 -C.sub.6 cycloalkyl, (CH.sub.2).sub.n --CH.sub.2 OH wherein n equals 1, 2 or 3, or R.sub.4 and R.sub.5 together represent (CH.sub.2).sub.m wherein m equals 4 or 5, or CH.sub.2 --CH.sub.2 --R.sub.6 --CH.sub.2 --CH.sub.2 wherein R.sub.6 represents O, NH or N--(C.sub.1 -C.sub.4) alkyl,
• X represents chlorine, bromine, iodine, hydroxy, acetoxy, trichloroacetoxy, trifluoroacetoxy, benzoyloxy, 4-nitrobenzoyloxy or --O--SO.sub.2 --R.sub.7 wherein R.sub.6 represents --CH.sub.3, --C.sub.6 H.sub.5 or --C.sub.6 H.sub.4 --CH.sub.3,
• the carbon atoms marked by an asterisk being both contemporaneously in the R or S configuration.